After New Yorker Alex Rein lost his job as a corporate lawyer in 2009, he decided to trade long hours reading contracts at his desk for... slushies. But not the neon, artificially flavored, convenience-store concoctions—he wanted to sell frozen treats that combined real pureed fruit with grown-up flavors like ginger and green tea. So using his own savings, plus money from friends and family, Rein, now 31, launched Kelvin Natural Slush, a food truck that hit the streets of New York City in the summer of 2010. It has since won a Vendy Award for best dessert and was named one of the top 20 food trucks in America by QSR magazine.  Here are the most important things he's learned about running a seasonal business. 

1. Anticipate obstacles. Rein planned to open the Kelvin truck for business much earlier than the actual July 2010 launch date. Getting the vehicle operational, making sure his staff had the proper food service licenses, and staking out a good location without infuriating the Mr. Softee trucks that already occupied the nearby streets all took longer than expected. "It was stressful," says Rein. "It took close to a year—longer than we thought, so it was a lot of running around, scrambling and learning as we went along. It took some time to figure out the best processes and the most efficient way to do things." 

2. Be flexible. Rein takes advantage of unexpected bouts of great weather by opening earlier and staying open later. Conversely, he has to deal with thunderstorms that leave his staff twiddling their thumbs. "The hours aren't any shorter than they were at the law firm," he says. "But it's more meaningful and rewarding when it's on your own terms." And while he prides himself on providing a unique product, he's open to partnering with another label to give his customers more ordering options: For example, he teamed up with Brooklyn-based ice cream company Blue Marble so he can offer slushie floats. 

3. Stay productive in the off-season. When the temperature drops and the slushie market dwindles come fall, Rein makes up the difference with catering jobs and corporate events. "We have an even more portable unit, which is just two slushie machines on wheels," he says. "So we can do catering and parties and just need a 115-volt outlet."